High expansion packers are used in through tubing applications where the packer or plug is then set in casing below the tubing through which it was delivered. Some designs provided cup shaped backup ring stacks that has staggered slots as between layers as an extrusion barrier in expansion ranges up to 25%. U.S. Pat. No. 6,827,150 is an illustration of one such design. Others are U.S. Pat. No. 7,128,145; US Publication 2004/0149429 and 2005/0115720. Other high expansion packer designs are U.S. Pat. No. Re 32,831; U.S. Pat. Nos. 6,311,778; 6,318,461 and 6,164,375.
The high expansion designs have focused on the need to prevent extrusion as a result of the combination of high expansion and differential pressure. The stack of backup rings were deformed against the surrounding tubular in a way that made the high expansion plug of the prior design removable by milling it apart. What has been needed in high expansion applications is a retrievable design that performs as needed to prevent element extrusion under pressure differentials typically seen for such plugs.
The present invention addresses this issue by using an overlapping petal design for the backup rings but disposing the rings in a manner where the assembly has a low profile for run in and that guides the flexing of the petals toward the surrounding tubular when in the set position. Support is offered to the petals by a housing on one side and a tapered guide ring on another side. As a result the petals elastically deform to act as a backup to the sealing elements and when the plug is unset and the sealing elements are able to release from the surrounding tubular using the stored potential energy from the elastic deformation that occurred when the plug was set. Minor image orientations of sealing elements and backup rings address differential pressures in opposed directions. Those skilled in the art will better understand the invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is determined by the claims appended below.